fix: cannot read getBoundingClientRect of undefined

fixes chrisbateman#15

Author: chrisbateman

src/shared/createVisualization.js

@@ -65,9 +65,10 @@ export default function createVisualization({svgElement, root, onHover, onUnhove
 
 
  var svgWrapper = vis[0][0];
+ 
  var visHeight = svgWrapper.getBoundingClientRect().height;
 
- var topPadding = (svgWrapper.getBoundingClientRect().top + window.scrollY) - (svgWrapper.offsetParent.getBoundingClientRect().top + window.scrollY);
+ var topPadding = (svgWrapper.getBoundingClientRect().top + window.scrollY) - (d3.select('.chart')[0][0].getBoundingClientRect().top + window.scrollY);
 
  d3.select(svgElement).attr('height', visHeight);
  vis.attr('transform', `translate(${chartSize / 2}, ${(chartSize / 2) - topPadding})`);